Comparison of Microwave Dielectric Properties of Ba0.6Sr0.4TiO3 Thin Films Grown on (100) LaAlO3 and (100) MgO Single-Crystal Substrates

The microwave properties of barium strontium titanate (Ba_0.6Sr_0.4TiO₃) thin films grown on (100) LaAlO₃ (LAO) and (100) MgO single-crystal substrates through the sol–gel technique were investigated. The interdigital capacitor (IDC) technique was used to measure the nonlinear dielectric properties in the frequency range from 1 GHz to 10 GHz. The results show that the Curie temperature, capacitance, and tunability of the films are strongly dependent upon the substrate. The film fabricated on the LaAlO₃ substrate has a higher tunability of 16.77% than that grown on the MgO substrate (～8.38%), measured at 10 GHz with an applied voltage of 35 V. The loss tangent is a linear function of the frequency in the microwave range, and the film grown on the MgO substrate has a lower loss tangent than that grown on the LAO substrate. This work reveals the great potential of Ba_0.6Sr_0.4TiO₃ (BST) films for application in tunable microwave devices.     

Distributed Flow Control and Medium Access in Multihop Ad Hoc Networks

Recent studies have shown that the performance of wireless multihop ad hoc networks is very poor. In this paper, we first demonstrate that one important reason of the poor performance is the close coupling between medium contention and network congestion. Therefore, we present a framework of distributed flow control and medium access control to address both medium contention and network congestion. The proposed scheme utilizes the MAC layer control frames to efficiently conduct the network layer's flow control function and only allows the upstream nodes to forward enough packets to make it possible for the downstream nodes to fully utilize the shared channel but never introduce severe MAC collisions and network congestion. Extensive simulations illustrate that the proposed scheme well controls congestion and greatly alleviates medium collisions. It achieves up to 12 times the end-to-end throughput of IEEE 802.11, maintains a short delay and a low control overhead, and improves the fairness regardless of the hop count and the traffic load     

Molecular Dynamics Simulation on Mechanics of Mg2Si Nanofilm

Molecular dynamics simulation has been carried out to study the mechanical properties of Mg₂Si nanofilm. For the binary thermoelectric material Mg₂Si with antifluorite crystal structure, a modified Morse potential energy function in which the bond-angle deformation has been taken into account is developed and employed to describe the atomic interactions to shed light on its mechanical properties. In the simulation, the radial distribution function of Mg₂Si nanofilm is computed to validate its crystal structure, and the stress–strain responses of the nanofilm are examined at room temperature. It is found that the mechanical properties of Mg₂Si nanofilm are quite different from those of bulk Mg₂Si due to the impact of surface atoms of the nanostructures. The size effect and the temperature effect on the mechanical properties of Mg₂Si nanofilm are discussed in detail.     

基于计量信息模型的电力计量自动化PI点维护方法

佛山供电局海量实时数据采用PI数据库进行存储,目前已经有270多万PI点,是全球首家超过200万点的厂家。目前对PI点的管理缺乏确实有效的方法,本文提出了一种基于业务模型的PI点自动维护方法,从模型同步、PI点创建、完整性检测、PI点清理四个方面实现PI点的自动维护,有效的保证了PI点的准确性、实时性和同业务模型的一致性。     

Low-Temperature Sintering of Ba0.5Sr0.5TiO3-SrMoO4 Dielectric Tunable Composite Ceramics for LTCC Applications

A sintering-aid system using melting of B-Li glass for barium strontium titanate (BST)-based compositions to be used in low-temperature cofired ceramic (LTCC) layers is introduced. The effects of the sintering aid on the microstructure, dielectric properties, and application in LTCC were investigated. The composition Ba_0.5Sr_0.5TiO₃-SrMoO₄ with 3 wt.% B-Li glass sintered at 950°C exhibits optimized dielectric properties, including low dielectric constant (368), low dielectric loss (0.007), and moderate tunability (13%, 60 kV/cm) at 10 kHz. At 1.44 GHz, it possesses a dielectric constant of 218 and Q value of 230. LTCC multilayer ceramic capacitors fabricated by the tape-casting process have steady relative tunability of 12% at 300 V, suggesting that BST50-SrMoO₄-B-Li glass composite ceramic is a promising candidate for electrically tunable LTCC microwave device applications.     

Phototunable Underwater Oil Adhesion of Micro/Nanoscale Hierarchical‐Structured ZnO Mesh Films with Switchable Contact Mode

Controllable surface adhesion of solid substrates has aroused great interest both in air and underwater in solving many challenging interfacial science problems such as robust antifouling, oil‐repellent, and highly efficient oil/water separation materials. Recently, responsive surface adhesion, especially switchable adhesion, under external stimulus in air has been paid more and more attention in fundamental research and industrial applications. However, phototunable underwater oil adhesion is still a challenge. Here, an approach to realize phototunable underwater oil adhesion on aligned ZnO nanorod array‐coated films is reported, via a special switchable contact mode between an unstable liquid/gas/solid tri‐phase contact mode and stable liquid/liquid/solid tri‐phase contact mode. The photo‐induced wettability transition to water and air exists (or does not) in the micro/nanoscale hierarchical structure of the mesh films, playing important role in controlling the underwater oil adhesion behavior. This work is promising in the design of novel interfacial materials and functional devices for practical applications such as photo‐induced underwater oil manipulation and release, with loss‐free oil droplet transportation.     

A Dilute Fluorinated Phosphate Electrolyte Enables 4.9 V-Class Potassium Ion Full Batteries

Potassium ion batteries using graphite anode and high-voltage cathodes are considered to be optimizing candidates for large-scale energy storage. However, the lack of suitable electrolytes significantly hinders the development of high-voltage potassium ion batteries. Herein, a dilute (0.8 m ) fluorinated phosphate electrolyte is proposed, which exhibits extraordinary compatibility with both graphite anode and high-voltage cathodes. The phosphate solvent, tris(2,2,2-trifluoroethyl) phosphate (TFP), has weak solvating ability, which not only allows the formation of robust anion-derived solid electrolyte interphase on graphite anode but also effectively suppresses the corrosion of Al current collector at high voltage. Meanwhile, the high oxidative stability of fluorinated TFP solvent enables stable ultrahigh-voltage (4.95 V) cycling of a potassium vanadium fluorophosphate (KVPO₄F) cathode. Using TFP-based electrolyte, the 4.9 V-class potassium ion full cell based on graphite anode and KVPO₄F cathode shows rather remarkable cycling performance with a high capacity retention of 87.2% after 200 cycles. This study provides a route to develop dilute electrolytes for high-voltage potassium ion batteries, by utilizing solvents with both weak solvating ability and high oxidative stability.     

晶粒度对纳米铜粉抗氧化能力的影响(英文)

以KBH4和维生素C(VC)为还原剂,以CuSO4·5H2O为原料,以EDTA为络合剂,PVP为分散剂,用液相还原法制备不同晶粒度的纳米铜粉。不同晶粒度的纳米铜粉同时在空气中放置1h后,进行XRD、DTA-TG以及TEM检测。结果表明:不同粒度的纳米铜粉在空气中抗氧化能力不同,晶粒度越大抗氧化能力越强。晶粒度大于75nm时在空气中放置1h不被氧化,平均晶粒度为75nm的纳米铜粉在120℃时开始氧化。纳米铜粉的熔点很低,进行TEM检测时,在电子束照射下颗粒熔融长大。     

舰载相控阵雷达的自适应波束扫描技术优化

为了提高舰载相控阵雷达的目标定位检测能力,提出一种基于二维波束域加权谱峰搜索的舰载相控阵雷达自适应波束扫描算法.采用均匀阵列构建舰载相控阵雷达相干分布源模型,以目标的方位及目标的扩展角为二维参量,建立点目标信号源的多亮点特征分布阵列,用点目标来模拟空间的分布式目标,采用自适应波束形成算法进行目标的方位、距离及DOA的联合参量估计,采用二维波束域加权谱峰搜索方法实现远场分布式目标的空间谱特征提取,根据谱峰的位置求出目标方位,实现对目标的自适应波束扫描,提高目标的定位检测能力.仿真结果表明,采用该方法进行舰载相控阵雷达的自适应波束扫描,对目标的定位准确率较高,检测性能较好,波束输出具有很好的旁瓣抑制能力,说明抗干扰能力较强.     

The Dynamic Behavioral Model of RF Power Amplifiers With the Modified ANFIS

The adaptive neuro-fuzzy inference system (ANFIS) has been widely used for modeling different kinds of nonlinear systems including RF power amplifiers (PAs). The modified ANFIS (MANFIS) architecture is simpler than that of ANFIS, but with nearly the same performance for modeling nonlinear systems. In this paper, the MANFIS is applied to model RF PAs with memory effects. The simulation and experimental results both in the time and frequency domains show that this model has good modeling accuracy and the characteristics of faster convergence and lower computational complexity compared with the ANFIS model. The normalized mean squared errors of the MANFIS model are slightly lower than those of some other neural network models such as the real-valued time delay neural network, radial basis-function neural network, etc. Finally, the MANFIS model is successfully used in a digital predistortion system, which can provide over 10- dB adjacent channel leakage ratio improvement for three-carrier wideband code division multiple access signals.